A fluorine-containing resin has excellent characteristics such as non-stickiness, stain resistance, heat resistance, chemical resistance, clearness, ultraviolet ray aging resistance, weatherability, and water and oil repelling property, which are not possessed by the other resins. However, the fluorine-containing resin is very difficult to be laminated on the other materials due to its non-sticking characteristic. Therefore, the fluorine-containing resin is not actually widely used in spite of the above-mentioned excellent characteristics. A tubular laminate is not an exception.
Effort to conduct lamination on a fluorine-containing resin molded article has been first directed to modification of a surface of the fluorine-containing resin molded article, and various modification methods have been developed. For example, there are known methods in which an electric discharge treatment such as corona discharge is conducted (JP-B-17485/1962, JP-B-51421/1984, JP-B-54848/1990, JP-A-214620/1984, JP-A-9533/1988, JP-A-218336/1988, JP-A-222838/1988), a method in which a flame treatment or a metallic sodium treatment is conducted (JP-B-10176/1988), a method in which surface roughing treatment is conducted by sand blast, and the like. In most cases, however, sufficient adhesion may not be obtained only by modifying the surface of the fluorine-containing resin. Therefore, an adhesive is used for lamination.
These methods are similarly applied to lamination of a tubular fluorine-containing resin molded article. JP-B-51421/1984 discloses a process for producing a tubular laminate in which after treating an outer surface of an inner layer of the fluorine-containing resin molded article by corona discharge, a rubber-based primer layer is formed on the treated surface, and an unvulcanized rubber sheet is wrapped on the primer layer, then vulcanization is conducted.
For forming the primer layer or the adhesive layer, however, more steps are necessary corresponding thereto. Further, various considerations are required for selection of the adhesive.
The present invention provides a process for producing a tubular fluorine-containing resin laminate without an adhesive layer (a primer layer) and having a strong adhesion to each other.